The Speed of Information

[savvos]

Is there a known physical law that constrains the speed at which information is transmitted to the speed of light? Could someone, for example, build a carbon nanotube or other pole-shaped extremely rigid substance with almost no compressibility with a length of several light seconds, push one end and have the information that the pole had been pushed arrive at the other end in less time than it would take a photon to travel the length of the pole? Or taken to an extreme, if you made a pole out of part of a neutron star and did the same experiment, would the information travel faster than the speed of light? Since the matter in a neutron star is supposed to be pretty much as compressed as matter can get before forming a black hole, the pole should not compress in a way that would prevent the information from arriving more slowly than the speed of light.

I know it would be impossible to construct any of the things mentioned above with current technology, but I am curious as to what a physicist would have to say about this thought experiment.

 

[BoJangles2]

Einstein says no.

With regards to matter under any normal circumstances, it would act in an elastic manner. As for a neutron star; though they are compressed, there is still another level of compression, and that’s a black hole.

If a neutron star hit another, would it set up a situation that broke the laws of relativity? No. Conservation of angular and linear moment, conservation of energy, E=mc^2, and everything else I’ve missed would just make a big explosion.

If a black hole hit another, would it set up a situation that broke the laws of relativity? No. As above it would make great viewing, but as far as physics tells us, it will still play by the physics handbook. Play 101, thou shalt not send information faster than the speed of light.

Well unless we don’t fully understand this part of physics properly yet; and if we don’t, unless we have evidence of such and a theory, best not worry about it.

 

[Vax]

Einstein is not god! there is hope for us FTL folk!

 

[BoJangles2]

Your right Einstein isn’t god, but he is experimentally correct.

Actually, there is no hope for you FTL folk, the boat has left and you have been stranded on woo-island.

 

[Jerromy]

Einstein is not god! God is God, and even God cannot send information faster than light. God is smart enough to send information so it arrives to the destination at the right time. God did not say "Let there be tachyons, and they were great", God said, "Let there be light, and it was good". If light isn't fast enough for all you FTL wanna bees then do better and PLEASE make a better Earth next universe.

On a realistic note... any matter that could be accelerated to the speed of light would be broken down into it's constitutent photons of electromagnetic radiation and since that always moves at the speed of light (no more and no less) there is no possible way to surpass that limit.

 

[Vax]

blasphemy

 

[Shpaget]

On a realistic note... any matter that could be accelerated to the speed of light would be broken down into it's constitutent photons of electromagnetic radiation and since that always moves at the speed of light (no more and no less) there is no possible way to surpass that limit.

savvos isn't talking about matter being accelerated to speed of light.
He's talking about pushing very long sticks at sub relativistic speeds.

 

[Boots09]

I recall watching an interview with Dr. Hawking, when asked about worm holes he said while they may be poss. any over 6" in dia. would probably be unstable. So, faster than light travel through one..no..but maybe a signal.

 

[Jerromy]

savvos isn't talking about matter being accelerated to speed of light.
He's talking about pushing very long sticks at sub relativistic speeds.

It doesn't matter how long the stick neither how dense. When you push matter it condenses. The more density that exists creates more mass to be pushed. The harder you push to accelerate matter the more it condenses where you concentrate the force. Suppose you have the lightest solid element in a nano-string, you push the first atom in line and the force causes a chain reaction along the string of atoms, the wave of motion between atoms cannot exceed the speed of light. As relativistic theory predicts the force between atoms to accelerate the next atom in the string to a velocity of the speed of light would take an infinite amount of energy.

To sum it up: there is no push hard enough, let alone matter dense enough to withstand such a push if it could be created. Faster than light was yesterday and tomorrow will be slower yet.

 

[azure_infinity]

OK, you have a rod exactly 1 light-second long. Call one end Point A and the other end Point B.

Your brain wants to tell you, because of everyday common sense, that Point A and Point B are intrinsically connected because they both belong to the ends of a connected rod. It's at this basic step that you're failing to understand.

Even though the rod is conected throughout, and the ends both belong to valid inertial frames, those inertial frames cannot be connected directly. It is the very fabric that makes up space-time that disconnects them.

If you push the rod, this is an event that occurred in the inertial frame at Point A. This "event" expands like a growing bubble in space-time. In one second, that "event bubble" will have expanded exactly one light-second in radius, allowing observers to witness the event one light-second away in distance. Whether the rod is connected or not, the event will not occur at Point B until exactly one-second after the event happened at Point A.

It is meaningless to explain any differently, here's why:

Say you have a witness sitting at Point B with a stop-watch, but you also have two other observers with stop watches. One observer is moving from Point A to Point B. The other observer will move from Point B to Point A. Because light travels at a constant speed regardless of your frame of reference, they will all witness the event occurr, but at different times. Even though this is the case, they are all considered valid observations.

 

[Shpaget]

Ok, I think the time is ripe for some real science.
The speed of the "push" can be calculated using the formula for longitudinal waves in solids:

More on this here.

 

[SpeedFreek]

See also:

http://math.ucr.edu/home/baez/physics/R ... FTL.html#4

If you have a long rigid stick and you hit one end, wouldn't the other end have to move immediately? Would this not provide a means of FTL communication?

Well, it would if there were such things as perfectly rigid bodies. In practice the effect of hitting one end of the stick propagates along it at the speed of sound in the material; this speed depends on the stick's elasticity and density. Relativity places an absolute limit on material rigidity in such a way that the speed of sound in the material will not be greater than c.

 

[colesakick]

Information has no speed limit guys.

Owing to the properties of space and quantum properties of entanglements; information is both ubiquitous and instantaneously communicated throughout the universe the moment it is created. To understand how this can be so and to picture how it works you need to know two things, what are quantum entanglements and what is information.

We know that quantum entanglements communicate instantaneously by perturbing one of two particles that were once quantumly entangled. Particle A can be removed to any Nth distance from particle B and no matter what you do to A (change its spin or energy state), B will reflect the same event/change without any elapse of time.

Information is more complicated to describe (refer to Leonard Susskind article in Scientific American mag. called the Holographic Universe) but we can see how it works at the quantum scale using holograms (a classical physicist will describe how this operates differently than a quantum mechanic. I will use the quantum description).

Using laser lights of differing frequencies an object that is to be filmed to create a holographic image is placed directly in line with laser A. Laser B is directed at the beam of light emanating from laser A. A snapshot is then taken using a special gel film that captures the trails of photons swirling all over the surface of the object photographed. The hologram is a record of the entanglements of all the photons that touched the object; as such it is a source of information.

HereYou can tear a hologram in half and have two complete images of the 3-D object. You can in fact tear the image any number of times and still have complete images on every scrap of film you make. This is so because each photon that “met” another during the imaging will forever and always “know” the placement/state of all the rest and will forever and always communicate that information.

As Leonard Susskind argues, the universe is holographic in nature and as such all information in it is as instantaneously communicated as the “action at a distance” particles and the trails of entanglements captured in a hologram described above. It is theoretically possible and if fact already demonstrated that we can glean information from location A about some location B of our choosing without any line of sight or other access to location B. We can take images of a man in another room (currently the image appears as a white ghost image but the USAF is still trying to perfect these quantum cameras) with current technology that exploits the iniquitousness of information.

 

[colesakick]

Continued from last:

The extrapolation of this reality is that we can choose to image distant stars and galaxies by translating the entanglements of photons in our own local space. All things that exist in the aether of space emit and absorb the waves of photons crisscrossing the universe and one another. Once entangled always entangled so the information is locally available no matter how long light has been traveling from location/object B.

http://www.spacedaily.com/reports/Ghost ... n_999.html

 

[azure_infinity]

Well, honestly, I share a little of your enthusiasm regarding Quantum Entanglement. We really can't, at this point, deny it's existance, and the potential is fascinating to me.

What you are suggesting is this: At some time in the near future, we may have quantum cameras. We could point these cameras at deep space objects. The Deep Space Object we want to see, say, we only see it from light that's 12 billion years old. If we use these quantum cameras, we can actually see an image of what the object looks like at present day because that information is already imprinted in the light signal. Light experiences zero time, yadayada. From a classical standpoint it would be like seeing 12 billion years into the future.

I guess I'm not going to rule that out or refute it for the moment.

So let's not mix up the two examples. We may someday have cameras that can see into the future, related to quantum entangled light sources. Cool, but I don't think that it should violate what we observe.

Coming back to the long pole thought experiment. (he he) The event occurring at Point A...moving the pole, could possibly be witnessed at Point B--if that person had a quantum entanglement telescope--exactly one second before the event occurs at Point B.

This and only this can describe what we already observe and not violate known laws. It just sounds too sci-fi for me.

 

[darkmatter4brains]

HereYou can tear a hologram in half and have two complete images of the 3-D object. You can in fact tear the image any number of times and still have complete images on every scrap of film you make. This is so because each photon that “met” another during the imaging will forever and always “know” the placement/state of all the rest and will forever and always communicate that information.
.

I think it's more correctly stated that a 3d image is stored on a 2d medium by interference of light waves. Since interference is not like a stream of 1s and 0s, or bits, which are the conventional digital way of storing information, but rather spread out on the medium, you can destory certain parts of that medium and not lose the overall image - you would only experience a degradation in resolution.

Fascinating subject guys. Hadn't thought of the Universe in these terms before. On a related note, apparently some neurologists are coming around to viewing the brain "holograhically" as well. They're having trouble isolating the locations of exactly where memory is stored - and finding that it's as if memories are stored over whole parts of the brain. very similar to your example above, and hence the term "the holographic mind" that I keep seeing. However, this is still highly controversial last time I looked into it.

if you want to get really far out there, does consciousness relate to entanglement at all?? Our synapses, etc., are on a realm small enough where it's possible quantum mechanical effects could come into play. In addition, could our mental pathways become entangled with another mind, allowing some sort of instantaneous connection over great distances - ala psyhic ability :lol:

What you are suggesting is this: At some time in the near future, we may have quantum cameras. We could point these cameras at deep space objects. The Deep Space Object we want to see, say, we only see it from light that's 12 billion years old. If we use these quantum cameras, we can actually see an image of what the object looks like at present day because that information is already imprinted in the light signal. Light experiences zero time, yadayada. From a classical standpoint it would be like seeing 12 billion years into the future.

Wouldn't it be more like 12 billion years into the present?

 

[Jerromy]

I feel as far as provable facts are concerned quantum entanglement is nothing more than misunderstood relationships between coexisting particles. A particle is created with a multi-axis spin and its anti particle is created with the opposite multi-axis spin. A proven fact is that the act of observing alters such particles and therefore observing the spin of one particle on a specific axis would be anagolous to observing the anti-particle and its opposite spin. Since the initial observation affects the electron and the positron no other meaningful observations can be conducted.

The "spooky action at a distance" can be easily understood as sending two identical messages to equidistant opposite positions and the observers at each recieving point would get the same information at the same time at distant locations. Oh, that is so spooky... it's just plain kooky.

 

[azure_infinity]

In some ways, we are all correct here. I know it is kinda silly to refer to light as "photons", since we have a quantified...quantised...er, quantum theory of light(phew!) now. For the sake of language, I will continue to refer to light in my thought experiments as "photons". By the way, quantum light theory does no more to explain the behavior than Special Relativity did. They're both unfinished works...obviously.

We have to be very careful what we are saying here. There is a distinctive difference between "Action at a distance" and "Information at a distance". The topic is "Speed of information". I wanted to clarify that there is a difference here, because while action-at-a-distance belongs squarely in the realm of classical physics, information-at-a-distance clearly does not these days.

The rigid rod is a classical experiment and should be treated as such.

Now that we are talking about light signals and QE, the subject is far more robust!

Let me explore Quantum Entanglement a little more, though:

Say we decide we want to see Alpha Centauri as it is today. The light we receive from Alpha Centauri is roughly 4 years old when it gets here.

We can NOT point a QE camera at Alpha Centauri to view into the future (present, into the present (Tx, Darkmatter4brains!)). We need to encode the light signal.

The rules say, interaction MUST take place between the camera and what is to be observed for the entanglement to take place. Currently we can view photons from Alpha Centauri, but since we can't decode the entangled pairs of photons that are (at present) leaving or interacting with the star, we can't gleen any information from the ones we get to interact with.

If we point a laser at Alpha Centauri, and wait 4 years for our laser to reach it, THEN and only then would we be able to use our QE camera.

You see, QE is very real, and very weird, but we STILL have to interact with the information in a classical way to get the information we are looking for. QE requires entangled pairs at minimum, we have to "touch" one half of the pair, while the other half is "interacting---at a distance".

In this way, classical observation is still conserved. QE cameras will never see deep space objects as they are in the present. Just more cosmic censorship.

This makes sense to me but I might be off somewhere in this, please speak up if I am.

 

[Fallingstar1971]

FADE IN......................................

Falling Star kneeling before an alter. "Dear God, please make me rich"
(thoughts are bio-energy limited to light speed)

Fallings prayer leaves. At light speed his prayer takes 15 billion years to get to the end of the visible Universe.

FADE OUT (commercial) (Are you the victim of a "prayer mail" scam? "I am a wealthy Angel who wants to move 1.2 billion blessings out of heaven.....")

FADE IN

Fallings prayer lands in Gods "In" box, turns out to be a light prayer load today so we can turn that around pretty quick for you. God promptly sends a response.

Gods response re-enters the Universe and begins its 15 billion light year journey back to Falling Star.

FADE OUT (commercial). (OxyClean, Billy May Hayes cleaning the shroud of Christ)

FADE IN Solar remnant, planetary nebula slowly expanding into space. Camera settles on a lump of rock about 1 AU from the center of the nebula.

Voice Booms in from space. "Dear Falling, after carefully reviewing your request, God says..........NO"

FADE OUT (To audience laughter)

The End

 

[azure_infinity]

geez, I just fell off my chair!

 

[SpeedFreek]

If we point a laser at Alpha Centauri, and wait 4 years for our laser to reach it, THEN and only then would we be able to use our QE camera.

You see, QE is very real, and very weird, but we STILL have to interact with the information in a classical way to get the information we are looking for. QE requires entangled pairs at minimum, we have to "touch" one half of the pair, while the other half is "interacting---at a distance".

In this way, classical observation is still conserved. QE cameras will never see deep space objects as they are in the present. Just more cosmic censorship.

An excellent post there, azure_infinity!

 

[azure_infinity]

Thanks, sir

 

[GreyMatters]

If we point a laser at Alpha Centauri, and wait 4 years for our laser to reach it, THEN and only then would we be able to use our QE camera.

You see, QE is very real, and very weird, but we STILL have to interact with the information in a classical way to get the information we are looking for. QE requires entangled pairs at minimum, we have to "touch" one half of the pair, while the other half is "interacting---at a distance".

In this way, classical observation is still conserved. QE cameras will never see deep space objects as they are in the present. Just more cosmic censorship.

An excellent post there, azure_infinity!

Brian Greene wrote in one of his books, I think Elegant Universe, of experiments of entangled photons where one half of the entagled photon was filtered and the other photon reacted as if filtered before the other photon was filtered relative to each photon's light cone. He said, at the time, that there was still no explanation as to why this was observed.

Einstien's theories have not been disproven, but the characteristics of entanglement and tunneling are not even poorly understood. So, to apply Einstien's theories to this phenomenom is incorrect when not knowing all of the characteristics.

Information can not travel from point A to B FTL, true. But:

1) Tunnelling particles may not be "moving" at all when changing their probabilistic postions for all we know.
2) Entangled particles may be connected on dimensions that we can't, as of yet, observe. The entanglement may be constant and have no distance in these dimensions. No particle can inhabit the same space at the same time, but I don't know of any law that says it can't inhabit two "spaces" at the same time. After all, an entangled photon IS "two" photons created from a single quanta of energy.

IMO anyway...

 

[SpeedFreek]

Brian Greene wrote in one of his books, I think Elegant Universe, of experiments of entangled photons where one half of the entagled photon was filtered and the other photon reacted as if filtered before the other photon was filtered relative to each photon's light cone. He said, at the time, that there was still no explanation as to why this was observed.

But of course, we can only know the other photon reacted before we interfered with its partner when we correlate the data with that of its partner at the end of the experiment. I think Greene was referring to the delayed choice quantum eraser experiment.

The Quantum Eraser Experiment.

http://en.wikipedia.org/wiki/Delayed_ch ... tum_eraser

 

[GreyMatters]

That does seem to be the experiment Greene was referring to in the book. Thanks for the link.

Has the experiment detailed in the accepted paper in Nature that comes to the conclusion that the influence, I read information, transmitted between entangled particles have a lower bound of 10,000 times the speed of light been refuted?

http://www.nature.com/nature/journal/v454/n7206/full/nature07121.html

Please let me know if this "influence" is still somehow obscured by relativity so that it is not somehow information. Also, isn't this influence the basis for the theories of Quantum Computing?